Automatic telephone system



Nov. 29, 1955 w. w. PHARIS 2,725,426

AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. 20, 1950 ll Sheets-Sheet l Mm MW MP Y R R mm mm w m w m M f M m w J w w A V m E 0 n w Z Q :5: v m 0@ w M Y m H w 1 W 0 M m L 6 mm 1 LOO/9L LINES Nov. 29, 1955 W. W. PHARIS 7/7/VDEM ll Sheets-Sheet 2 OFF/CE HTTO/P/VEY Nov. 29, 1955 w. w. PHARIS AUTOMATIC TELEPHONE SYSTEM 11 Sheets-Sheet 4 Original Filed Jan. 20, 1950 FIG.4

II SELECTOR BANK 0 LEVEL ,HSB

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C.D.0. INC. SEL. BANK I LEVEL LEVEL 7 INVENTOR. WILL/AM W. PHARIS E/z INC. SEL.

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2 WAY REPEATER TANDEM OFF/CE ATTORNEY Nov. 29, 1955 w. w. PHARIS 2,725,426

AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. 20, 1950 11 Sheets-Sheet 5 LINE FINDER AND SEL. CIRCUITS /3 TO INC. SEL.

BANKS NOTE.

THIS HS LEAD SWITCHES FROM T0 DURING THE DIAL/N6 OF EACH DIGIT OF H A rou. CALL AND DURING CONTROLLED I RINGING FROM TOLL BOARD 34 INVENTOR. WILLIA M W. PHARIS 0-) FIG. 5 CONNECTOR By ATTORNEY Nov. 29, 1955 w. w. PHARIS AUTOMATIC TELEPHONE SYSTEM 11 Sheets-Sheet 6 Original Filed Jan. 20, 1950 IMON NOTE. THIS WIRE CONNECTS TO P.U. COMMON INA CODE RINGING SYSTEM TO INTERCEPT CIRCUIT SLO W OPERATE GENERATOR SOURCES lg-(fl TO INTERRUPTED E W W '0 6 R '0 INVENTOR. WILLIAM W. PHARIS ATTORNEY CONNECTOR FIG. 6

Nov. 29, 1955 w. w. PHARIS 2,725,426

AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. 20, 1950 ll Sheets-Sheet '7 HSTA SEL. BANKS TOLL WITH AUTOMATIC SENDING SEL. BANKS FREE SERVICE SEL. BANKS TOLL WITHOUT AUTOMATIC SENDING INC. SEL.

TO CONNECTOR 2-WAY F.S. AND TOLL REPEATER C. D. O.

INVENTOR. FIG 7 WILLIAM W. PHARIS ATTORNEY Nov. 29, 1955 w. w. PHARIS 2,725,426

AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. 20 1950 11 Sheets-Sheet 8 I 8R5 2-WAY F.S. AND TOLL REPEATER C D O L:I*'W\/() P62 INVENTOR.

(+) WILLIAM W. PHAR/S 8 jz fiwew ATTORNEY Nov. 29, 1955 w. w. PHARIS 2,725,425

AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. 20, 1950 ll Sheets-Sheet 9 I57 ISRS SLOW I OPERATE Z-WAY F.S. AND TOLL REPEATER C. D. O.

INVENTOR. FIG. 9 WILLIAM W. PHARIS BYJZM ATTORNEY Nov. 29, 1955 w. w. PHARIS Y 2,725,426

AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. 20, 1950 11 Sheets-Sheet 10 INVENTOR.

(-) WILLIAM w. PHARIS 2-WAY F.S. AND TOLL REPEATER BY e TANDEM FIG. '0 ATTORNEY Nov. 29, 1955 w. w. PHARIS 2,725,426

AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. 20, 1950 11 Sheets-Sheet 11 R m E can M 7 I M M K I O E CN' 0 c R E 6 J L H I J A? My L BY H M S B B B B 8 W RTS S H c W I I I I INVENTOR.

WILLIAM PHARIS ATTORNEY I I (H -I I I I .I I I I I I I I I I I I I 2 WAY ES. AND TOLL REPEATER H 76 67 5 007 9 I4 5 I 2 6 22% 64 6 WWW M $W M Z Z M l I f TANDEM OFFICE United States Patent AUTOMATIC TELEPHONE. SYSTEM William W. Pharis, Rochester, N. Y'., assignor to Stromberg Carlson Company, a corporation-of New York Original'application. January 20, 1950, SerialNo. 139,632,

now Patent No. 2,678,355, dated- May 11, 1954. D1- vided and this application March 25, 1952,.Seri'al No. 279,089

6 Claims. (Cl. 1'79'--16)' This is a division of my copendiug application Serial No. 139,632, filed January 20, 1950', now Patent No. 2,678,355, granted May 11, 1954.

This invention relates to telephone systems in-general, but is concerned more particularly with telephone systems including a toll ofiice, a community dial ofiice (C. D. O.) and a tandem office, inter-connected withtrunk lines and arranged to provide several desired? features and to give more efiicient and satisfactory service.

The broad general object of the invention is the provision of new and improved circuit arrangements for use in trunk circuits, repeater circuits and connector circuits in a tandem oflice network as illustrated in the trunking diagram of Figs. 1 and2 of the accompanying drawings.

An additional and more specific object of the invention is the provision of a new repeater circuit in the tandem ofiice which, in handling a call from the C. D. O. to the toll office, automatically sends the digit necessary for extending the call from the tandem oflice to the distant toll office. This makes it possible to use regular inter-office trunks for toll calls from there'mote C. D. 0., through the tandem office to the distant toll office and permits the use of a universal numbering plan for toll', that is, the usual digit 0 is dialled in the C. D'. O'. for selecting a trunk to the tandem ofiice, after which the call is extended from the tandem office, through an incoming selector associated with the C. D. O.tandem ofiice trunk, to a trunk leading to the toll ofiice. The same C. D. O.-tandem ofiice trunks are used for free service calls between C. D. 0. subscribers and tandem ofiice subscribers, these trunks-when selected in the C. D. 0. from a local level (not level 0) omitting the automatic sending operation.

Another feature of the invention is the employment of the conventional pulse correction circuit for the additional purpose of this automatic sending operation. The trunk from the C. D. O. to the tandem office is provided with several paths of access and that one which is seized when the call is to be automatically forwarded through the tandem ofiice to the distant toll ofiice contains a relay responsive to the seizure of that path. The repeater contains a trigger circuit which is cocked on the seizure of the repeater over this path and is only released when the toll operator answers, and in its release conveys certain information to the toll' operator. This trigger circuit responds to the above said relay and transmits a signal to the pulse correction circuit which is then cut off by the action of the trigger circuit in operating a companion relay which latter relay besides terminating this signal' to the pulse correction: circuit also cuts off the first said relay. Thus the pulse correction circuit is given a fillip and will respond by transmitting a digit (digit 1- consisting of a single pulse) to the distant directively operated incoming switch.

Another feature of the present invention relates to the provision of a marking conductor in the repeater and connector circuits for marking tollcalls to provide the above mentioned operation, this same marking conductor being also used for transmitting supervision between the. different stages in the system.

General description Figs. 3 and 4 are circuit diagrams of the 2-way trunk repeater on the tandem ofiice end of each 2-way trunk be tween the toll ofiice and the tandem othce.

Figs. 5 and 6 are circuit diagrams of the combination local and toll connector inthe tandem ofiice forproviding the necessary circuit operations in a connector of this type. The new and novel'features of this connector'circuit are claimed in the co-pending application of Kessler and Frankel, Serial No. 139.701, filedJanuary 20, 1950.

Figs. 7, 8 and 9 are circuit diagrams of the 2-way'repeater on the'C. D. O; office endof each 2-way trunk between the C. D. 0. an'd'the tandem ofiice.

Figs. 10 and 11' are circuit diagrams of the 2-way repeater on the tandem ofiice end of each 2-way trunk between the tandem oflice and the C. D. 0'.

Fig. 12 is'a chart showing how to arrange the circuit figures to show the complete system;

The trunking diagram, shown in Figs. 1 and 2, has been chosen to illustrate the invention as arranged to meet the requirements of a specific installation, wherein local lines in'the C. D. O. are multipled to the banks of line finders and connectors in the-usual'manner. The line finders have their associated first selectors, the second level of which connects to local connectors for establishing local calls in the C. D. O. Traffic between the C. D. O. andthe tandem ofiicepa'sses over 2-way trunks, one of. which is shown connecting the 2-way repeater in the C. D: O. with the 2-way repeater in the tandem ofiice. An incoming selector is associated with each 2-way repeater in the C. D. O. for handling calls incoming thereto, the second level of the incoming selectors being multipled to the second level of the first selectors foraccess to the connectors in thisoffi'ce. There are two paths of access from the local first selectors to therepeaters inthe C. D. 0., the first path being from level 8 for free service calls by directory number operation (no automatic sending) and the second path. being from level 0 for handling calls in response to dialling 0 in the C. D. 0., this latter operation effecting the automatic sending'in the 2-way repeater in the C. D. 05.

A free service and toll repeateris associated with each 2'-way' trunk in the tandem ofiice and handles calls from the C. D. O. to the tandem ofiice when the associated trunk is selected at level 8 or level 0 in the C. D. 0. An incoming selector is associated wtih each repeater in the. tandem office for handling calls from the C. D. 0.

It is proposed to provide a 2-way repeater in the toll.

ofiice and in the tandem ofiice on each inter-office trunk between these ofiices. Each of these trunks terminates on a jack at the toll position in the toll ofiice, to which connection is made by the usual plug and cord, to which the dial may be connected for dialling subscribers? num bers in the tandem office and in the C. D. O. by way ofthe repeater and associatedincoming selector on the terminating end of each inter-office trunk.

The capacity of the tandem office is illustrated as being 200' lines, since two connector groups are shown, one being selected from the third level and the other being selected from the sixth level of all selector groups in this ofiice. The local lines in the tandem office are connected to first selectors by means of associated line finders for calls originating in this ofii'ce. The first level of the local first selectors is used for special. calls such as information, complaint, wire chief and the like. The seventh level of all the tandem office selectors extends to the 2'-way repeaters of the trunks to the C. D. O. for free service calls from the tandem ofiice to the C. D. O. The. first level of the incoming selectors on the tandem- Da 0. inter ofiice trunks is multipled to the 0 levelof 3 the local first selectors for the purpose of extending a call from the C. D. O. to the toll office when the automatic sending operation is effected in the repeater in the C. D. 0., in response to the selection of this repeater by a C. D. O. subscriber dialling for a toll call.

It is believed that the invention will best be understood by describing in detail certain circuit operations involved in establishing calls of different classes. Due to the fact that a major portion of the circuit operations provided in the present system relates to repeater operation, it will be convenient to separate these circuit operations into different groups and to provide a heading for each group.

For the purpose of simplifying the illustrations and facilitating the explanation, the various parts and circuits constituting the embodiment of the invention have been shown diagrammatically and certain conventional illustrations have been employed, the drawings having been made more with the purpose of making it easy to understand the principles and mode of operation than with the idea of illustrating the specific construction and arrangement of parts that would be employed in practice. Thus, the various relays and their contacts are illustrated in a conventional manner, with all of the contacts associated with a particular relay being illustrated as attached to this relay by means of a dashed line. The negative side of the common exchange battery is indicated by a minus sign in parentheses and the positive side of the exchange battery, which is usually grounded, is indicated by a positive symbol in parentheses.

T all-tandem ofiice call It will first be described how the repeater 0n the tandem oflice end of a toll-tandem ofiice trunk operates, this repeater being illustrated in Figs. 3 and 4. When the toll operator plugs into the jack associated with the interofiice trunk, the repeater associated with this trunk (not shown in detail) functions to close a loop circuit across the trunk conductors leading to the tandem ofiice. Since this operation is old and well known in the art, the detailed circuits in the toll office will not be shown or described. This closure of the trunk conductors effects the operation of relay PL in the repeater in the tandem ofiice over a circuit which may be traced from upper winding of relay PL, upper left hand winding of repeating coil RC, break contact of relay CB, tip trunk conductor TT extending to the toll office, through the closed circuit path provided in the repeater on the trunk in the toll office, ring trunk conductor RT, break contact of relay CB, lower left hand winding of repeating coil RC and lower Winding of relay PL to The operation of relay PL closes a circuit for operating relay RD2 extending from make contact of relay PL and winding of relay RDZ to Relay RD21 is now operated over a circuit extending from make contact of relay RDZ, break contact of relay RD1 and winding of relay RD21 to Relay RD21 makes this trunk busy to outgoing calls from the tandem ofiice to the toll office by applying potential to conductors SB and 18B leading to the bank multiple of the selectors over a circuit extending from make contact of relay RD21 and conductor 116 to the bank multiple of the first selectors. The circuit to the incoming selector associated with the repeater in use is now closed, this circuit being traced from conductor 111, which is the tip conductor leading to the incoming selector, make contact of relay RD21, upper right hand Winding of repeating coil RC, make contact of relay RD21, resistor 1R8, make contact of relay RD21, lower right hand winding of repeating coil RC, make contact of relay PL, make contact of relay RD21 and conductor 112 to the incoming selector. Although the detailed circuits of the incoming selector are not shown, it will be obvious that conductors 111 and 112 extend through break contacts of switching relay SW in the incoming selector to the windings of a CB relay and thence to and The CB relay operates over this closed circuit, operates its associated RD or holding relay and prepares the incoming selector for the first series of impulses.

It will now be assumed that the toll operator dials digit 3 to set the incoming selector on the third level and to select a connector in this level. These three impulses are repeated by relay PL, since the three impulses from the dial into the repeater in the toll office effect this repeater to repeat these three impulses into the repeater in the tandem office. The first release of relay PL in Fig. 3 opens up the above-described circuit including conductors 111 and 112 for providing the first impulse in the incoming selector. The release of relay PL also closes an operating circuit for relay SH which may be traced from break contact of relay PL, make contact of relay RD21 and winding of relay SH to The closure of the uppermost make contact of relay SH shortcircuits the right hand windings of repeating coil RC to remove the impedance of these windings from the impulse circuit to the incoming selector. It will be noted that resistor 2R8 and condenser C1 are connected across the make contacts of relay PL, thus providing a spark. absorbing circuit for these contacts during impulsing. When relay PL operates to mark the end of the first impulse, the trunk circuit to the incoming selector is closed at the make contact of relay PL for marking the end or" this impulse in the incoming selector by closing a circuit across conductors 111 and 112. Relay SHI is operated at this time over a circuit which may be traced from make contact of relay PL, break contact of relay SHl, make contact of relay SH and winding of relay SH1 to Relay SI-Il is locked operated over a circuit extending from make contact of relay SHl, make contact of relay SH and winding of relay SHI to When relay PL releases to mark the beginning of the; second impulse, conductors 111 and 112 are again opened and are closed when relay PL operates to'mark the end of the second impulse. When relay PL releases to mark the beginning of the third impulse, conductors 111 and 112 are opened and are again closed when relay PL operates to mark the end of the third impulse. Consequently, the incoming selector is stepped to the third level in response to these three impulses transmitted from the toll operators position. During the intermittent operation of relay PL, the winding of relay SH is de-energized but this relay does not release during impulsing, due to its slow acting characteristics. When relay PL remains operated at the end of the impulse transmission for this digit, relay SP1 is de-energized long enough to permit it to release for removing the short-circuit from the right hand windings of the repeating coil. The release of relay SH opens up the above-described circuit to the winding of relay SH1 for eifecting the release of this relay. The remaining digits of the number are dialled by the toll operator and relays PL, SH and 8H1 function in the manner just described for each digit, relays SH and 81-11 being operated at the beginning of the digit and released at the end of the digit. These remaining impulses are effective to impulse the selected connector, it being understood that the incoming selector selects an idle connector following the receipt of the first digit. This connector operation will be later described.

Particular attention is now called to the fact that the operation of relay SHl disconnects from the left hand terminals of relay HS and connects to these terminals, the circuit to extending through a make contact of relay RD21 and a make contact of relay 8H1. Conductor 113, extending to the incoming selector, is connected to through resistor BRS during the operation of the selector, consequently relay HS is not operated because the circuit to (above described) energizes both windings of this relay in opposition as indicated by the arrows associated with the windings of the relay. This alsoapplies to the operation during the remaining digits, since conductor 113 is extended by way of wiper HS of the incoming selector to conductor HS incoming t the connector, this HS conductor being normally connected to through a resistor for preventing the operation of the HS relay during dialling.

When the called party answers, conductor HS incoming to the connector is switched from to (as will be pointed out in describing the connector operation), thus operating relay HS of the repeater, since only its upper winding is now energized from this circuit to by way of the upper winding and break contact of relay SH1 to This switch from to when the called party answers is provided by contacts on the AA relay in the connector. The operation of relay HS connects to the winding of relay RD2 to hold this relay energized for in turn maintaining relay RD21 energized to maintain potential on conductors SB and 18B to keep this trunk busy at the selector banks as long as the called party is on the line. This holding of the RD2 and RD21 relays also holds the circuit while the called party is on the line, conductors 111 and 112, extending to the connector circuit, being closed by way of the above described circuit including resistor IRS. The operation of relay HS closes a circuit for operating relay CB which may be traced from lower Winding of relay CB, conductor 118, resistor 4R8, make contact of relay HS, conductor 119 and upper Winding of relay CB to The operation of relay CB reverses the battery to the toll trunk for supervisory purposes. The operation of relay CB also disconnects the spark absorbing circuit including resistor ZRS and condenser C1 from across the right hand winding of the repeating coil RC for removing the transmission loss in the circuit which would otherwise be efiected by this spark absorbing circuit.

When the conversation is terminated and the operator releases the connection, the repeater in the toll ofiice opens up the inter-oflice trunk conductor for releasing relay PL at the tandem ofiice repeater and this relay in turn opens up and releases relay RD2. Relay RD2 opens up and releases relay RD21, this latter relay disconnecting from conductors SB and ISB for rendering this trunk idle to outgoing calls from the tandem oflice to the toll office. The release of relay P-L closes the above described circuit for operating relay SH and this relay is opened up and released when relay RD21 releases. This momentary operation of relay SH is of no eifect. When the called party hangs up the receiver, the HS conductor incoming to the connector is switched back to consequently the windings of the HS relay are de-energized for eifecting the release of this relay, which in turn opens up and releases relay CB for straightening out the battery to the toll ofiice to give the toll operator unhook supervision.

On an outgoing call from the tandem oflice to the toll ofiice, the calling party in the tandem oflice dials 0 for advancing the first selector (not shown) to the tenth level for selecting a 2-way repeater associated with an idle trunk leading to the toll ofiice. When the selector seizes the selected repeater and operates its switching relay for switching the calling line circuit through to the repeater in the tandem oflice, the closed circuit across the calling line operates relay CB in the repeater illustrated in Fig. 3. This circuit may be traced from lower winding of relay CB, break contact of relay RD21, upper right hand winding of repeating coil RC, tip trunk TB leading to the selector bank, through the selector, line finder, line circuit and over the calling line and substat-ion circuits in series, back through the line circuit, the line finder and the selector to conductor RB, break contact of relay RD21, lower right hand winding of repeating coil RC, break contact of relay RD21 and upper winding of relay CB to The operation of relay CB reverses the battery by way of the windings of relay PL to the trunk circuit leading to the toll office for operating the proper relay in the repeater circuit associated with this trunk in they toll oflicefor signalling the toll operator,

in the well-known manner. The operation of relay CB also opens up the circuit including resistor ZRS and condenser C1 for removing this spark absorbing circuit from the repeating coil circuit to eliminate any loss in transmission which would be involved in the conversational circuit if this spark absorbing circuit was left across the repeating coil.

The operation of relay CB closes a circuit for operating relay RD1 extending from break contact of relay RD21, make contact of relay CB and winding of relay RD1 to The operation of relay RD1 applies potential to the incoming sleeve conductor SB for making this trunk busy to other selectors and to provide a holding circuit for the switches used in this call. This circuit may be traced from break contact of relay CT 1, conductor 120, make contact of relay RD1 and conductor SB. Coin box tone relay CT is noW operated over a circuit extending from break contact of relay RD2, make contact of relay RD1, conductor 121 and winding of relay CT to Relay CT closes an obvious circuit for operating relay CTl. The operation of relay CTl disconnects direct from the above described circuit extending back to conductor SB, thus inserting the lower winding of tone coil TC in this holding circuit. The operation of relay CT1 also applies ring back tone to the calling line over a circuit which may be traced from the source of ring back tone RBT, condenser C2, break contact of relay SH1, conductor 122, make contact of relay CTl, conductor RB and back over the calling switches to the calling line circuit.

When the operator answers by plugging the answering plug into the incoming trunk jack, the normally closed high resistance path in the trunk conductors is reduced in the repeater in the toll ofiice (not shown) to a low resistance value in the well-known manner for permitting sufiicient current to flow over the loop trunk circuit for operating relay PL in Fig. 3. The operation of relay PL closes a circuit for operating relay RD2 extending from make contact of relay PL and winding of relay RD2 to Relay SH1 is operated at this time over a circuit extending from make contact of relay PL, break contact of relay SH1, make contact of relay RD1 and winding of relay SH1 to Relay SH1 closes a locking circuit for itself which may be traced from make contact of relay SH1, make contact of relay RD1 and winding of relay SH1 to The operation of relay SH1 opens up the above described circuit to conductor RBT for disconnecting the ring back tone from the calling line as an indication that the operator has answered the call. The operation of relay RD2 opens up the above described circuit for relay CT for efiecting the release of this relay which in turn opens up and releases relay CTl. During the interval between the operation of relay SH1 and the release of relay CTI, the coin box tone circuit is connected to the conductors of the trunk to indicate to the toll operator if the calling line is a paystation line. This circuit may be traced from the right hand terminal and upper winding of coil TC, make contact of relay CT1, conductor 123, make contact of relay SH1, conductor 122, make contact of relay CTI, conductor RB, break contact of relay RD21 in multiple with make contact of relay PL, lower right hand winding of repeating coil RC, condenser C3, upper right hand winding of repeating coil RC, make contact of relay RD2, conductor 124, make contact of relay CT1 and condenser C4 to the left hand terminal of the upper winding of coil TC. As is well known in the operation of paystation circuits, a paystation of coin box line has a source of coin box tone connected to the sleeve conductor of this line, thus extending this circuit through the uppermost make contact of relay RD1 to the lower winding of coil TC. Consequently during the interval between the operation of relay SH1 and the release of relay CTl, this coin box tone (if the calling line is a paystation line) is induced into the upper winding of coil TC for application to the trunk circuit as above described.

After the conversation to the distant toll office is terminated and the calling party hangs up the receiver, the opening up of the calling line circuit opens up and releases relay CB of Fig. 3. This straightens out the battery connected to the inter-office trunk circuit for giving the distant operator on hook supervision. Now when the operator takes down the connection, the circuits at the toll ofiice function to again switch the loop trunk circuit from a low resistance to a high resistance value for effecting the release of relay PL of Fig. 3. The release of relay PL opens up the above described circuit for relay RDZ for effecting the release of this relay, after which the above described circuit to relay RDl is opened, this circuit being established to lock relay RDl when relay RD2 was operated. The release of relay RDl disconnects potential from conductor SB for releasing the incoming switches and for marking this trunk idle for other connections. The release of relay RDl also opens up the above described circuit to relay 8H1 for releasing this relay. This restores the circuits to normal ready for another call.

C. D. O.tandem ofiice trunk call It will now be described how the inter-office trunk circuits operate on a call originated in the C. D. O. of Fig. 1 and terminated in the tandem office of Fig. 2. The 2-way repeater located at the C. D. 0. end of the trunk circuit is illustrated in Figs. 7, 8 and 9 and the 2-way repeater associated with the tandem office end of the same trunk circuit is illustrated in Figs. 10 and 11. Before describing the operation of the circuits in response to an originating call in the C. D. 0., it will be helpful to point out the normal condition of the interoffice trunk circuit, describing how the and terminals of the common batteries in each office are normally connected to the trunk conductors so that no current flows over the conductors of a trunk circuit during the normal condition. Starting with the repeater in the tandem ofiice (Figs. 10 and 11) the normal battery circuit may be traced from lower winding of relay CB2, conductor 126, break contact of relay R1312, upper left hand winding of repeating coil RC, break contact of relay SR2, tip toll line conductor TL to the C. D. 0., break contact of relay SR2 in the C. D. O repeater (Fig. 9), upper right hand winding of repeating coil RC, break contact of relay RD11, conductor 128, break contact of relay SH and winding of impedance coil CB22 to the terminal of the battery in this office. Returning to the tandem oflice repeater circuit, the minus terminal of the battery in this office is connected to the upper winding of relay CB2 and extends by way of conductor 127 and a break contact of relay R1312, lower left hand winding of repeating coil RC, break contact of relay R1312, break contact of relay SR2 and toll line conductor RL to the C. D. O. From this conductor in the C. D. 0., the circuit may be traced through a break contact of relay SR2, conductor 129, break contact of relay RD1, conductor 13%, lower right hand winding of repeating coil RC, break Contact of relay RD11, and winding of relay CB21 to It will be thus seen that, during the normal condition of the circuits, the same terminals of the batteries at each end of the trunk circuit are connected together by way of the various relay windings, contacts and trunk line conductors so that no current normally flows over the trunk circuit.

Now when the calling party on the calling line in the C. D. O. removes the receiver and dials the proper digit into the first selector to which the calling line is connected by the line finder in the Well-known manner, the first selector advances to the selected level (level 8 for selecting a free service call to the tandem oifice in this example) for extending the calling line conductors to the 2-Way repeater associated with the first idle interofiice trunk in the C. D. 0. When this repeater is selected, the closed circuit across the calling line operates relay CB1 of the C. D. O. repeater over a circuit which may be traced from upper winding of relay CB1, break contact of relay R1321, conductor 131, upper left hand winding of repeating coil RC, conductor 132, break contact of relay SR11, tip conductor TFS leading to the free service bank terminals in the selector, through the first selector, line finder, line circuit and substation circuit in series, back over the ring conductor of the circuits and conductor RPS in the repeater, break contact of relay SR11, conductor 133, lower left hand winding of repeating coil RC, conductor 134, break contact of relay R1321, and lower winding of relay CB1 to Relay CB1 closes a circuit for operating relay RDI extending from make contact of relay CB1, and winding of relay RDI to The operation of relay R131 primes relay PS to make it fast operating when its operating circuit is closed, this priming circuit extending from make contact of relay RDl, high resistance MRS, conductor 135, break contact of relay CT, break contact of relay GT1, break contact of relay TD1, break contact of relay TD2 and winding of relay PS to Relay RD1 also applies potential to the incoming sleeve conductor SP8 to which the selector and finder circuits are connected, for making this repeater busy and for holding the preceding circuits, this circuit being traced from break contact of relay CT2, conductor 137, make contact of relay RDl and conductor SFS. This conductor is also multipled to conductors STA and ST leading to other selector levels for making this trunk circuit busy in these other levels if and when used. The monitor lamp MON associated with the C. D. O. repeater is now lighted to give the switchboard attendant an indication that the repeater has been seized and that the call has not been answered. It will be later explained how the monitor lamp circuit is de-energized when the call is answered. It will also be understood that other monitor lamps associated with other repeaters may have their battery feed terminals connected through a low resistance relay, instead of being connected directly to as indicated, so that this relay may be operated in response to a call for operating coin box tone circuits and the like. The circuit for lighting lamp MON may be traced from break contact of relay SR, make contact of relay R131, conductor 138 and lamp MON to Relay S1112 is operated at this time over a circuit extending from make contact of relay RD1, conductor 139 and lower winding of relay SR12 to The circuit is now closed for operating relay R1311 which may be traced from make contact of relay SR12 and winding of relay RD11 to The operation of relay R1311 primes relay SR so that it will be operated when the battery is reversed over the toll line in response to the answering of the call and to prevent the operation. of the SR relay when battery flows in the normal direction over the toll line before the call is answered. This priming circuit may be traced from make contact of relay SR12, make contact of relay RD11, conductor 140, high resistance 9R3 and lower winding of relay SR to The operation of relay RD11 energizes the toll line trunk over a circuit which may be traced from lower winding of relay CB2 in the tandem oflice repeater, conductor 126, break contact of relay RD12, upper left hand winding of coil RC, break contact of relay SR2, toll line conductor TL, break contact of relay SR2 in the C. D. O. repeater, upper right hand winding of coil RC, make contact of relay R1311, conductor 141, make contact of relay RDl, upper winding of relay SR, conductor 142, resistor 1.2RS, make contact of relay R1311, lower right hand winding of coil RC, conductor 13%, break contact of relay RC2, break contact of relay SR1, conductor 129, break contact of relay SR2, toll line conductor RL, break contact of relay SR2 in the tandem office repeater, break contact of relay RD12, lower left hand winding ofcoil RC, break contact of relay RD12, conductor 127 and upper winding of relay CB2 to It willbe seen that the toll trunk is now energized through the upper winding of relay SR in the C. D. O repeater in series with the associated resistor 12RS. The energization of the upper Winding of relay SR over this circuit is in opposition to the energization of the lower winding so that relay SR does not operate at this time.

Relay FS now receives full current for operating over a circuit, which may be traced from make contact of relay RD11, conductor 143, conductor 135, break contact of relay CT, break contact of relay CTl, break contact of relay TDl, break contact of relay TDZ and winding of relay PS to Relay FS closes a locking circuit for itself which may be traced from this same at the make contact of relay RD11, conductors 143 and 135, make contact of relay FS, break contact of relay TDl, break contact of relay TD2, and winding of relay PS to Relay CT is now operated over a circuit which may be traced from make contact of relay RD11, conductor 143, break contact of relay SR1, conductor 144, make contact of relay FS and winding of relay CT to Relay GT1 isnow operated over a circuit extending from on conductor 135, make contact of relay CT and winding of relay CT1 to Relay CTl closes an obvious circuit for operating relay CT2. It will be noted that the operation of either relay CT or CTl opens up the above described operating circuit for relay FS, but that this latter relay remains operated over its previously described locking circuit. This places the circuits in the C. D. O. repeater in condition for receiving the impulses of the first digit.

The relay operations in-the tandem ofiice repeater will now be described. The closure of the toll trunk by way of the windings of relay CB2 in the tandemoffice repeater efiects the operation of this relay and it in turn closes a circuit for operating relay RD2 which may be traced from make contact of relay CB2, conductor 145 and winding of relay RDZ to A circuit is now closed for operating relay RD21 which may be traced from make contact of relay RD2, break contact of relay RD11 and upper winding of relay RD21 to Relay SR in the tandem ofiice repeater is now primed over a circuit which may be traced from make contact of relay RD21, resistor 15RS and upper winding of relay SR to The trunk to the incoming selector associated with the repeater in the tandem ofiice is now energized of a circuit which may be traced from through a winding of the CB relay associated with the selector (not shown), break contact of relay SW in the incoming selector, conductor 211, make contact of relay RD21, upper right hand winding of coil RC, make contact of relay RDZll, resistor 14RS, lower winding of relay SR, break contact of relay SH, make contact of relay RD21, lower right hand winding of coil RC, make contact of relay RDZ, make contact of relay RD21, break contact of relay SR2, conductor 146, break contact of relay PC2, conductor 21Z'and break contact of relay SW t the other winding of the CB relay in the incoming selector. It will be seen that the lower winding of relay SR in the tandem ofiice repeater is energized in series with resistor MRS over this circuit extending to the incoming selector. The energization of this winding of the SR relay is in opposition to that of the upper winding so that the relay does not operate at this time.

The operation of relay RD21 makes this 2-way trunk busy in the banks of the selectors in the tandem oifice to calls outgoing to the C. D. O. by applying to conductor SB over a circuit which may be traced from make contact of relay RD21, conductor 147 and conductor SB leading to the sleeve or test terminals in the seventh level of the selector banks, it being assumed that this is the level for selecting trunks on calls from. the tandem office to the C. D. O. The monitor lamp as- 10 sociated with the repater in the tandem ofiice is lighted over a circuit which may be traced from break contact of relay SR, make contact of relay RD21 and lamp MON to The energization of conductors 2 11 and 212 tending. to the incoming selector operates the associated CB and RD relays (not shown) and the RD relay of this selector applies back over conductor 213 for holding the RD21 relay over a circuit which may be traced from. conductor 213, make contact and lower winding of relay RD21 to This places the circuits of the repeater and the incoming selector in the tandem ofiice in condition for. receiving the firstv digit.

Referring back to the C. D. O. repeater, it will be assumed that the calling party dials 3 for advancing the incoming selector in the tandem ofiice to the third level for selecting a connector in the local connector group for extending a call to a line in this group. These three impulses are repeated by relay CB1 of the tandem ofiice repeater, since this relay is energized over the calling line. During the intermittent operation of relay CB1, relay RDl is de-energized but is not released because of its slow acting characteristics. Anadditional energizing circuit is completed to the winding of relay RD1 during the operation of pulse repeating relay PC2 (later described) by Way of a circuit extending fromv make contact of relay PCZ, make contact and winding of relay RD to this circuit assisting in holding the RDl relay operated during the impulsing operation of the'CBl relay.

The first release of relay CB1 closes a circuit for operating relay PC1 which may be traced from break contact of relay CB1, make contact of relay RD1, conductor 143, break contact of relay CB2 and upper winding of relay PC1 to Relay PC1 closes a circuit for operating relay SH extending from make contact of relay PC1 and winding of relay SH to Relay SH, at its uppermost make contact short-circuits the lower right hand winding of coil RC and at its second uppermost make contact short-circuits the upper winding of relay SR for improving the impulse repeating circuit to the distant tandem ofiicef The other contacts on the SH relay are used in connection with a call in the other direction over the trunk circuit. When relay CB1 operatesto mark the end of the first impulse acircuit is closed for operating relay PCZ which may be traced from upper winding of relay PCZ, make contact of relay PC1, break contact of relay PCZ and upper winding of relay PC1 to Relay PC]. is locked operated over this circuit including the upper winding of relay PCZ', it being noted that the circuit to direct to the upper winding of relay PC1 above described, is opened when relay CB1 operates. Now when relay PC2 operates the above described locking circuit for relay PC1 is opened and this relay is released. It releases after a short predetermined time interval because its lower winding is short-circuited when the relay is operated and because of the adjustable shunt across its upper winding provided by resistor 6R8. The operation of relay RC2 closed a locking circuit for itself extending from upper winding of relay PC2, make contact of relay PC1, make contact and lower winding of relay PCZ to this locking circuit being opened by the release of relay PC1 for opening up and releasing relay PCZ. Relay PC2 is timed in its release operation by the connection of shunt resistor SRC across its lower winding.

Now when relay CB1 releases to mark the beginning of the second impulse, relay PC1, is operated over the previously described circuit and when relay CB1 operates to mark the end of the second impulse, relay PC1 is locked, relay RC2 is operated and locked, after which relay PC1 is released and then relay PC2 is released, all in the previously described manner. Furthermore, when relay CB1 releases to mark the beginning of the third impulse, relay PC1 is again operated and when relay PC1 operates to mark the end of the third impulse relay PC1 is locked operated, relay PC2 is operated and locked,

after which relay PC1 is released for releasing relay PCZ in the previously described manner. During the release of relay PC1, the circuit of relay SH is de-energized but this relay does not release due to its slow acting characteristics until the end of the impulses of this digit, at which time relay PC1 remains released for a sufficiently long interval to eflect the release of relay SH.

During the intermittent operation of relay PC2, the toll trunk line is impulsed. At each operation of relay PC2 the above described circuit, including the toll line conductors, is opened at the uppermost break contact of this relay and is closed at this contact when the RC2 relay is released. When relay SH releases to mark the end of the digit, the above described short circuit across the windings of relay SR and coil RC is removed.

Referring now to the tandem ofiice repeater, each impulse in the toll trunk (open circuit condition) effects the release of relay CB2 connected to this trunk circuit. Consequently relay CB2 repeats the impulses transmitted by relay CB1 in the C. D. O. by the dialling operation. Relay RD2 in the tandem oflice is not released during the intermittent operation of the CB2 relay because of its slow acting characteristics. The first release of relay CB2 in the tandem office repeater closes a circuit for operating relay PC1, this repeater extending from break contact of relay CB2, conductor 149, make contact of relay R1321, conductor 150, break contact of relay PC2 and upper winding of relay PC1 to Relay PC1 closes a circuit for operating relay SH extending from make contact of relay PC1, break contact of relay SR1, conductor 151 and winding of relay SH to Relay SH short circuits the lower right hand winding of the repeating coil RC in the tandem ofiice repeater and connects the ring side of the circuit leading to the incoming selector (conductor 212) by way or" the impulsing contacts of relay PCZ, conductor 1% and break contact of relay SR2, make contacts of relays RD21 and RS2 in series, make contact of relay SH, make contact of relay R1321, make before break make contact of relay SH, make contacts in series of relay R1321 and conductor 211 to the incoming selector, thus removing the windings of all coils in the repeater so that the impulse circuit to the incoming selector, through contacts of the PC2 relay may lead direct over a circuit with all impedances and resistances removed from this circuit.

The operation of relay CB2 at the end of the first impulse effects a locking circuit for relay PC1 and an operating circuit for relay PCZ which may be traced from make contact of relay R1321, conductor 147, upper winding of relay PCZ, make contact of relay PC1, break contact of relay RC2 and upper Winding of relay PC1 to Relay PC2 operates and opens up the above described circuit including relay PCl for effecting the release of this latter relay, While relay PC2 is locked operated until relay PC1 releases over a circuit extending from make contact of relay R1321, conductor 147, upper winding of relay PC2, make contact of relay PC1, make contact and lower Winding of relay PC2 to When relay CB2 releases to mark the beginning of the second impulse, relay PC1 is operated and when relay PCP. operates to mark the end of the second impulse, relay PCl is locked and relay PCZ is operated and locked, after which relay PC1 releases for eifecting the release of relay PC2, all in the previously described manner. When relay CB2 releases to mark the beginning of the third impulse, relay PCl is again operated and when relay CB2 operates to mark the end of this impulse, relay PC1 is locked, relay PC2 is operated and locked and relay PC1 is released for eltecting the release of relay PC2, all in the previously described manner. It will thus be seen that relay PCZ. repeats the impulses provided by relay CB2, this latter relay repeating the impulses received from the distant ofiice. When relay PC1 releases to mark the end of the last impulse of the digit, it remains in its released position long enough to effect the release of relay SH for again including the windings of the SR relay and the repeating coil in the circuit to the incoming selector.

Since the lowermost break contact of relay PC2 is included in the circuit to the CB relay of the incoming selector, the intermittent operation of relay PC2 impulses the incoming selector in accordance with the received impulses for advancing the selector to the third level in this example. When the incoming selector advances to the selected level and connects with the selected trunk in this level, the above described closed circuit across conductors 251 and 21.2, including the lower Winding of relay SR and the windings of repeating coil RC, is completed for operating the impulse relay in the selected connector. Before describing the operation of the connector (Figs. 5 and 6) it will be explained how the repeaters operate in response to the answering of the call and in response to the release of the connection.

It may be helpful to point out at this time how the circuits, including the toll line conductors, are energized before the called party answers. Beginning with the lower winding of relay CB2 in the tandem ofr'lce repeater, extends through this winding, conductor 126, break contact of relay RDlZ, upper left hand winding of coil RC, break contact of relay SR2, toll line conductor TL, break contact of relay SR2 in the C. D. O. repeater, upper right hand winding of coil RC, make contact of relay RDll, conductor 141, make contact of relay RDl, upper winding of relay SR, conductor 14-2, resistor HRS, make contact of relay RDH, lower right hand winding of coil RC, conductor 13h, break contact of relay PCZ, make contact of relay CB1, conductor 129, break contact of relay SR2, toll line conductor RL, break contact of relay SR2 in the tandem otfice repeater, break contact of relay RD12, lower left hand winding of coil RC, break contact of relay RDItZ, conductor 127 and upper winding of relay CB2 to Since this circuit includes the resistances of the CB2 relay, the toll line conductors, the upper winding of relay SR in the repeater in the tandem office and the resistor 12RS, suificient current flows to hold relay CB2 operated. However, the current flow over this circuit is in the normal direction over the toll line and prevents the operation of relay SR of Fig. 8.

When the call is answered in the tandem ofiice, the connector answering relay reverses the battery back over conductors 211 and 212 and since the lower winding of relay SR is included in this circuit, the reversal of the battery connection efiects the operation of relay SR. A circuit is now closed for operating relay SR2 which may be traced from make contact of relay SR, break contact of relay RD12 and winding of relay SR2 to The operation of relay SR also opens up the above described circuit for lamp MON for extinguishing this lamp. The operation of relay SR2 reverses the circuit, including the toll line conductors extending to the windings of relay CB2, thus causing a reverse current flow over the toll line and since the upper winding of relay SR in the C. D. O. repeater is included in the toll line circuit, this relay operates and closes a circuit for operating relay SR1 extending from make contact of relay SR, conductor 152, make contact of relay R1311, conductor 153, and winding of relay SR1 to Relay SRllll is also operated at this time over a circuit which may be traced from make contact of relay SR, conductor 152, make contact of relay RDH, break contact of relay TA, conductor 154, break contact of relay T132, conductor 155 and winding of relay SRTll to The operation of relay SRll reverses battery back to the calling line for supervisory purposes. The operation of relay SR1 connects a bridge across the impulses contacts of relay PC2 in the C. D. O. repeater and switches the incoming conductor HSFS from at the break contact of relay SR1 to at the make contact of relay R1311 for supervision of this HS lead when provided.

in order to transmit a coin box tone from a calling paystation line to the distant office on this call, for the purpose of indicating that it is a calling paystation line if the call goes to an operator, the tone coil shown in the left hand portion .of Fig. 7 is connected across the toll line circuit by way of a path which may be traced from the lower terminal of the left hand winding of the tone coil, make contact of relay CTZ, conductor 156, make contact of relay SR1, break contact of relay SR11, conductor 132, upper left hand winding of coil RC, conductor 131, break contact of relay RDZ-l and upper winding of relay CB1 to (-1-). The upper terminal of the left hand winding of the tone coil may be traced by way of condenser C5, make contact of relay CTZ, conductor RFS, break contact of relay SR11, conductor 133-, lower left hand winding of coil RC, conductor 134, break contact of relay RD21 and lower winding of relay CB1 to Itwill be understood that the tone flowing through the left hand windings of coil RC is induced into the right hand windings of this coil and connected to the toll line over-the previously described circuit to which the right hand windings of this repeating coil are connected. it will also be understood that the right hand winding of the tone coil picks the tone oil of the incoming sleeve conductor SFS from the sleeve conductor of a paystation line While relay CTZ is operated to include the right hand winding of the tone coil in the holding circuit connected to conductor SFS. Now when relay SR1 operates in response to the answering of the call, the above described circuit to relay CT is opened for eifecting the release of this relay and the consequent release of relays CTl and CT2 by opening up their above described circuits. When relay CT2 is released, direct is again applied to conductor SP5 and the left hand winding of the tone coil is disconnected from the toll line circuit for moving the coin box tone.

When the call is answered in the distant oifice, the talking circuit is completed by way of the toll line conductors, with talking battery being fed to the called line from the connector in the tandem oflice and with battery being fed to the calling line from the windings of relay CB1 in the C. D. O. repeater.

It will first be assumed that the called party hangs up first. This straightens out the battery connection from the connector in the tandem oflice for reversing the current flow through the lower winding of relay SR of Fig. for effecting the release of this relay. The release of relay SR opens up and releases relay SR2. The release of relay SR also closes the energizing circuit for lamp MON as an indication to the attendant that the called party has hung up the receiver but that the connection is being held by the calling party, the circuit to the lamp extending from (I), break contact of relay SR, make contact of relay RDZl and lamp MON to Furthermore, the release of relay SR2 straightens out the battery connection to the toll line conductors TL and RL and since the upper winding of relay SR in Fig. 8 is in this toll line circuit, this reversal of current eifects the release of relay SR. The release of relay SR opens up and releases relays SR1 and SRH. The release of relay SR of the C. D. O. repeater also lights the monitor lamp in this circuit as an indication that the connection is being held by the calling party after the called party has hung up, this circuit being traced from (-1-), break contact of relay SR, make contact of relay RD conductor 133' and lamp MON to The release of relay SRll straightens out the battery to the incoming circuit to the C. D. O. repeater for providing supervision and the like in the well known manner. The release of relay SR1 also switches the incoming conductor HSFS from to for supervisory purposes when provided by way of this conductor.

Now when the calling party hangs up the receiver, relay CB1 of the C. D. O. repeater will be released for effecting the release of relay RDl. The release of relay RD1 opens up and releases relay SR12 andv this relay in turn opens up and releases relay RD11. The release of relay RDI opens up the above described circuit to lamp MON for extinguishing this lamp. The release of relay RD11, with relay RD1 released, disconnects from sleeve conductor SP8 for effecting the release of the selector, the finder and the line circuit used on the originating connection and for rendering this repeater idle. The release of relay RD11 restores the conductors of the toll trunk to their previously described normal condition so that this trunk is de-energized and the relays at each end of the trunk which are connected theretoare not operated. Relay P8 of the C. D. O. repeater is released when relay RD11 releases to open up the above described operating and locking circuits for the FS relay.

When the toll trunk conductors are de-energized, relay CB2 of the repeater in the tandem office is released for elfecting the release of the associated RD2 relay. The release of relay RD2' opens up the ring side of the trunk (conductor 212) extendingto the incoming selector, for effecting the release of the incoming selector and the connector used in connection with this call. When, the selector and connector are released, is disconnected from sleeve conductor 213 for opening up the above described locking circuit, including the lower winding of relay RDZI, for effecting the release of this relay. The release of relay RDZI' opens up the above described circuit to lamp MON for extinguishing this lamp. This leaves the circuits in normal condition ready for another call.

It will now be described how the circuits operate in case the calling party hangs up while the called party is still on the line. The circuits will be in the talking condition as above described and when the calling party hangs up the receiver, relay CB1 of the repeater in the C. D'. O. will be released for opening up and releasing relay RDl. The release of relay CB1 also opens up the toll line trunk for effecting the release of relay CB2 of the repeater in the tandem oflice and this relay in turn opens up and releases relay RDZ. The release of relay CB1 in the C. D. O. repeater closes the previously described circuit for operating relay PC1, this relay closes the previously described circuit for operating relay SH and when relay RD1 is released, the potential is removed'from the connection between the two upper windings of the PC1 and PC2 relays, thus efiecting the operation ofrelay PC2 and the locking of relay PC1 through these upper windings. The operation of relay PC2 opens up and releases relay PC1 for in turn opening up and releasing relays PC2 and SH. This operation of the PC2 relay is of no effect at this time because the toll line is now energized through the resistor 13RS. The release of relay CB2 in the tandem ofiice repeater closes the previously described circuit for operating relay PC1 and this relay again operates relay SH. Now when relay RDZI is released (as will next be described) the circuit to (l) for the upper windings of the PC1 and PC2 relays is opened, consequently relay PC2 does not operate. The release of relay PC1 opens up and releases relay SH, this momentary operation of the PC1 relay being'of no effect at this time. The operation of relay SH short circuits the operating (upper) Winding of relay SR for releasing this relay and this relay in turn opens up and releases relay SR2. The release of relay SR2 straightens out the battery connection to the toll line for reversing the current flow through the lower winding of relay SR of the repeater in the C. D. O. for effecting the release of this relay, which in turn opens up and releases relays SR1 and SRll.

When the toll trunk line is opened up by the release of relay CB1 of the repeater in the C. D. 0., and the consequent release of relay RDl, relay SR12 of this repeater is held operated over a circuit which may be traced from lower winding of relay CB2 of the repeater in the tandem ofiice, conductor 126, break contact of relay RD12, upper left hand winding of coil RC,

15 make contact of relay SR2 (or break contact of this relay after it releases as previously described), toll line conductor RL, break contact of relay SR2 of the repeater in the C. D. 0., conductor 129, break contact of relay RDl, conductor 1.30, lower right hand winding of coil RC, make contact of relay RDll, another make contact of relay RDlft, upper winding of relay SRlZ, resistor 13RS, conductor 157, break contact of relay RDl, conductor 141, make contact of relay RDll, upper right hand winding of coil RC, break contact of relay SR2, toll line conductor TL, make contact of relay SR2 of the repeater in the tandem omce (or break contact of this relay after it releases), break contact of relay RDIZ, lower left hand winding of coil RC, break contact of relay RDlZ, conductor 127 and upper winding of relay CB2 to It will be understood that this same circuit is completed with relay SR2 operated or released,

the only difierence being that battery flows over the trunk in one direction while the SR2 relay is operated and in the opposite direction when the SR2 relay is released, I

but the upper winding of relay SR12 is energized in series aiding relation to the lower winding while the battery is reversed over the toll line trunk for holding relay SRlZ operated. The high resistance coil 13RS in the toll line trunk at this time is sufiicieut to allow relay CB2 of the repeater in the tandem oflice to release as above described. Now when relay SR2 is released in response to the release of relay CB2 which operates relays PCT and SH, the battery is straightened out to the toll line conductors for reversing the flow of current :1

through the upper winding of relay SR12 of the repeater in the C. D. O. for releasing this relay. Relay SR12 opens up the operating circuit for the R1311 relay and this relay is released after relay SH is released for opening up a locking circuit for relay RD11 which may be traced from break contact of relay TA, conductor 158, make contact of relay SH, conductor 159, make contact and winding of relay RD11 to The release of relay RDll disconnects potential from sleeve holding conductor SFS for releasing the circuits used in extending the call to this repeater and for rendering the repeater idle.

The release of relay RDI closes a circuit for again energizing lamp MON which may be traced from make contact of relay RDlll, conductor 160, break contact of relay RDl, conductor 138 and lamp MON to this circuit being opened by the release of relay R1311 tor xtin uishing the lamp. Relay FS of the C. D. O. repeater is released when relay RDll releases for opening up the above described energizing circuit for the F5 relay. This restores the circuits of the C. D. G. repeater to normal and releases the connection extending to this repeater.

Referring to the repeater in the tandem ofiice, the release of the CB2 and RD2 relays, in response to the insertion of the high resistor 13RS in the toll trunk opens up the circuit to the incoming selector, including conductors 211 and 212, for effecting the release of the switches in the tandem oflice used in extending this call. When the switches release and remove from sleeve conductor 213, the locking circuit for the RD21 relay is opened for eifecting the release of this relay. The monitor lamp associated with this repeater is momentarily energized by the release of relay SR over a circuit extending from break contact of relay SR, make contact of relay RDZI and lamp MON to this circuit being opened when relay RDZl releases as above described.

When the switches in the tandem ofiice are released, while the called party is still on the line as in this example, the called line circuit either goes to its lockedout condition (if a line lock-out circuit is provided) or the connector (last party release) is held as long as the called party has the receiver off the hook.

l 6 Tandem ofizce-C. D. O. trunk call It will now be explained how the circuits function when a subscriber in the tandem office dials the seventh level (for example) for selecting the 2-way repeater in the tandem oflice associated with an idle trunk leading to the C. D. 0. When the closed circuit of the calling line is extended through the line finder and the first selector to the terminals leading to the 2-way repeater on the tandem otfice end of the 2-way trunk circuit, relay CB1 of this repeater is operated over a circuit which may be traced from upper winding of relay CB1, conductor 161, break contact of relay RD21, upper right hand winding of coil RC, conductor 163, break contact of relay SRll, tip trunk conductor TB leading back to the local first selector, through the selector, line finder, line circuit and substation in series, back through the line circuit, line finder and first selector to conductor RB, break contact of relay SR1, conductor 164, lower right hand winding of coil RC, break contact of relay RD21, conductor 162 and lower winding of relay CB1 to Relay RD]; is now operated over a circuit extending from make contact of relay CB1, conductor 165 and winding of relay RDI to The operation of relay RD]. closes a circuit for priming relay SR so that it will be sensitive to current flow through its lower winding, when this flow of current is in the reverse direction, as will be later explained. This priming circuit may be traced from make contact of relay RDI, high resistor lfiRS and upper winding of relay SR to Relay RDl also applies potential to the incoming sleeve conductor SE for holding the preceding switches and for making this trunk busy to other calls. This circuit may be traced from make contact of relay R131 and conductor SB to the bank terminals of the selector group. A circuit is now closed for operating relay RD11 which may be traced from make contact of relay RDl and winding of relay RDll to Relay RD11 closes an obvious circuit for operating relay RD12. The monitor lamp is now lighted as an indication to the attendant that the repeater has been seized by a calling party and that the call has not been answered. The circuit for this lamp extends from break contact of relay SR, make contact of relay RD12 and lamp MON to The toll line conductors are now energized by way of a circuit which may be traced from winding of impedance coil C1322 of the repeater on the C. D. 0. end of this trunk circuit, break contact of relay SH, conductor 128, break contact of relay RDll, upper right hand winding of coil RC, break contact of relay SR2, toll line conductor TL, break contact of relay SR2 of the repeater in the tandem office, upper left hand winding of coil RC, make contact of relay RD12, resistor 16RS, lower winding of relay SR, break contact of relay SH, make contact of relay RD12, lower left hand winding of coil RC, conductor 166, break contact of relay PC2, break contact of relay SR1 and make contact of relay CB1 in multiple therewith, conductor 167, make contact of relay RDl, break contact of relay SR2, toll line conductor RL, break contact of relay SR2 of the repeater in the C. D. 0., conductor 129, break contact of relay RDl, conductor 130, lower right hand winding of coil RC, break contact of relay RD11 and winding of relay CB2! to Relay CB21 operates, closes a circuit for operating relay RD2 extending from make contact of relay CB21 and winding of relay RD2 to Relay RD2 makes this trunk busy to outgoing calls from the C. D. O. by applying potential to the sleeve terminals of the selectors which have access to this trunk. This make-busy circuit may be traced from make contact of relay RD2 and terminal SP8 to the bank contacts of the above mentioned selectors. The monitor lamp associated with the C. D. O. repeater is now lighted over a circuit which may be traced from break contact of relay SR, conductor 168, make contact of relay RDZ and lamp MON to this being" an indication to the attendant in the C. D. O. that the repeater has been seized but the call has not been answered. Relay RD21 of the C. D. O. repeater is now operated over a circuit which may be traced from break contact of relay RD11, make contact of relay RD2, conductor 169 and winding of relay RD21 to The operation of relay RD21 closes a priming circuit for the SR relay of this repeater which may be traced from make contact of relay RD21, high resistor 9RS and lower winding of relay SR to The operation of relay RD21 closes a circuit across the tip and ring conductors leading to the incoming selector associated with the repeater in the C. D. 0., including conductors 114 and 115. This circuit may be traced from through a winding of the CB relay (not shown) of this incoming selector, break contact of the selector switching relay SW, conductor 114, make contact of relay RD21, conductor 132, upper left hand winding of coil RC, conductor 131, make contact of relay RD21, upper winding of relay SR, resistor 11RS, make contact of relay RDZI, conductor 134, lower left hand winding of coil RC, conductor 133, make contact of relay RD21, break contact of relay PC2 and conductor 115 to the other Winding of the CB relay of the incoming selector. The CB relay of the incoming selector operates and closes a circuit for operating the associated RD relay to prepare the selector for receiving the next series of impulses.

It will be assumed that the calling subscriber dials digit 2 to advance the incoming selector in the C. D. O. to the second level for selecting a connector associated with an idle terminal in the selected group. Relay CB1 of the tandem ofiice repeater repeates the impulses from the dial and at the first release of this relay a circuit is closed for operating relay PC1 which may be traced from break contact of relay CB1, conductor 170, make contact of relay RD12, conductor 150, break contact of relay PC2 and upper winding of relay PC1 to Relay PC1 closes a circuit for operating relay SH which may be traced from make contact of relay PC1, break contact of relay SR1, conductor 151 and winding of relay SH to When relay CB1 operates to mark the end of the first impulse, a circuit is closed for operating relay PC2 and for locking relay PC1 which may be traced from make contact of relay RDl, conductor 147, upper winding of relay PC2, make contact of relay PC1, break contact of relay PC2 and upper winding of relay PC1 to It will be understood that this circuit is effective because the circuit to +1 from the break contact of relay CB1 (above traced) connected to the point between the upper windings of the PC1 and PC2 relays, is opened to permit the operation of relay PC2 and the locking of relay PC1. The operation of relay PC2 opens up the above described locking circuit for relay PC1 for effecting the release of this relay. Relay PC2 is locked operated until relay PC1 is released by way of the above described circuit including its upper Winding, make contact of relay PC1, make contact and lower winding of relay PC2 to With relays PC1 and PC2 released, the next release of relay CB1 to mark the beginning of the second impulse operates relay PC1 again and when relay CB1 operates to mark the end of the second impulse, relay PC2 is operated, relay PC1 is locked and when relay PC2 operates, the locking circuit for relay PC1 is opened for releasing this latter relay, after which the locking circuit for relay PC2 is opened for releasing the PC2 relay, all in the previously described manner. Since this is the end of the impulse for this digit, relays PC1 and PC2 remain released and relay SH is released, this latter relay being maintained operated during the pulsing of the PC1 relay because of its slow acting characteristics.

During this impulse operation, the tip conductor TL of the toll line is opened at the break contact of the continuity spring combination of relay SH and maintained open until relay SH releases and closes up this break contact. The operation of relay SH also applies potential to the ring conductor RL of the toll line over a circuit which may be traced from break contact of relay SR, break contact of relay RD21, make contact of the continuity spring combination of relay SH, make contact of relay RD12, lower left hand winding of coil RC, conductor 166, break contact of relay PC2, break contact of relay SR1, conductor 167, make contact of relay RD1 and break contact of relay SR2 to conductor RL. It will be seen that the break contact of relay RD12 which is connected to the lower terminal of the lower left hand winding of coil RC opens up the direct connection from toll line conductor RL normally extending to this terminal of this repeating coil winding, so that the break contact of the RC2 relay is inserted in this toll line conductor for impulsing purposes. Consequently, when relay PC2 operates, as above described, to repeat the impulses from relay CB1, the toll line conductor RL is opened for repeating these impulses over a single conductor of the toll line trunk circuit.

Referring now to the repeater in the C. D. 0., each opening of toll line conductor RL effects the release of relay CB21, consequently relay CB21 repeats the impulses applied to the toll line conductor RL. When relay CB21 releases to mark the beginning of the first impulse, a circuit is closed for operating relay PC1 which may be traced from break contact of relay CB21, make contact of relay RD2, conductor 148, break contact of relay PC2 and upper winding of relay PC1 to Relay PCl closes an obvious circuit for operating relay SH. Relay SH short-circuits the upper winding of relay SR, it short-circuits the lower right hand winding of coil RC, thus removing this winding from the toll line conductor, and it connects toll line conductor TL to the lower winding of relay TA to determine if this is a toll call. This connection of toll line conductor TL to the lower winding of relay TA may be traced from conductor TL, break contact of relay SR2, upper right hand winding of coil RC, break contact of relay RD11, conductor 128, make contact of relay SH, conductor 171, make contact of relay RDZ and lower winding of relay TA to Since it is assumed that this is not a toll call, the TA relay will not be operated over this circuit. It will be explained later how relay TA is operated when a call from the toll oflice is extended by way of the incoming selector associated with the toll-tandem ofiice trunk to the repeater connected to the seventh level of this selector in the tandem oflice.

When relay CB21 operates to mark the end of the first impulse of this digit, a circuit is closed for operating relay PC2 and for locking relay PC1, this circuit extending from upper winding of relay PC2, make contact of relay PC1, break contact of relay PC2 and upper winding of relay PC1 to When relay PC2 operates, the above described circuit to the upper winding of relay PC1 is opened for effecting the release of this relay. Also, when relay PC2 operates, it is locked operated until relay PC1 is released over a circuit extending from upper winding of relay PC2, make contact of relay PC1, make contact and lower winding of relay PC2 to When relay CB21 releases to mark the beginning of the second impulse of this digit, relay PC1 is again operated and when relay CB21 operates to mark the end of this impulse relay PC1 is locked and relay PC2 is operated. Relay PC2 effects the release of relay PC1 and this latter relay opens up and releases relay PC2, all in the previously described manner. When relay PC1 remains down to mark the end of the impulse of this digit, relay SH releases and removes the shortcircuit from the repeating coil and the upper winding of relay SR and switches toll line conductor TL from the TA relay winding back to the Winding of impedance coil CB22. 

